Click here for Overhead Construction Menu

Click here for IPOEE article No. 154 - wooden poles - 1933

Click here for an extract from British Telcom Engineering - 1985

Pole testing

The mainstay of GPO overhead construction was the pole.  Wooden poles were first used on telegraph lines around 1836 and the GPO have used since nationalisation of the telegraph service in 1870.  Originally made of wood, metal beams were used during the 1st Work War and metal poles at the end of the 2nd World War.  In the 1970's GRP types were introduced and are still used in certain circumstances, but the wooden pole covered all contingencies and are still in use to this day.

Wooden Poles
Metal Poles
Fibre Glass Poles
Poles, Overhouse and Standards
IPOEE No. 154 - The Telegraph Pole (1933)

Wooden Poles

Engineering Instructions
Issue 2, 2l.5.3

Preservative Treatment, Distinguishing Marks, and other details

1. Timber
The poles used in the service of the British Post Office are almost exclusively of Scots Pine (Pinus Sylvestris), generally known as Red Fir. The specification provides that the timber should be sound, hard grown (that is, with the annual rings closely pitched), straight, and free from large or dead knots or other defects; that the trees should be felled between the beginning of November and the end of February; and that each pole should retain the natural butt, sawn "square" after the timber has been felled. Other species of timber are occasionally used.

2. Home-grown timber
Some degree of relaxation in the interpretation of the specification is allowed in favour of suppliers of home-grown timber and, consequently, poles which depart from straightness to a greater extent than is allowed in the case of foreign timber are accepted from time to time. Such poles are unsuitable for erection in places where concession to existing amenities is essential. Requisitions for poles for erection in these localities should, therefore, be endorsed accordingly; efforts will then be made to meet the requisition by the issue of specially-selected poles.

3. Preservation
Poles are preserved from decay by seasoning, and by the injection of antiseptics into the sap-wood. The object of seasoning is not only to effect the drying up of the sap, which would otherwise be liable to encourage decay, but in many processes the object is to free the cell spaces, in order to permit of the efficient entry of the preservative solutions. Seasoning alone cannot be relied upon for the preservation of the poles used for line construction; they are subjected, therefore, to a preservative treatment.

4. Creosoting
The preservative used by the Department is Creosote, distilled from Coal Tar. Until 1912, poles were treated by the "Bethel" or "full cell" process, in which the poles are subjected to a vacuum to remove air from the cells and heated creosote is then introduced under pressure until no more can be absorbed. With this process, it is specified that a minimum of 12lb. of creosote per cu. ft. of pole shall be retained, and the poles usually retain a black oily appearance due to the excess of creosote. Since 1912 the "Ruping" or "Empty Cell" process has been used. In this process the poles are first subjected to air pressure, creosote is then forced into the pores under greater pressure, and finally a vacuum is applied which, assisted by the expansion of the air initially forced into the cells, removes all creosote in excess of that required to coat the cell walls. Approximately 4lb. of creosote is retained per cubic foot of pole. The colour of the poles when so treated is dark brown, and the surface can be painted when quite dry.

5. Creosoting (after cutting poles for arms, etc.)
Whenever a creosoted pole is cut for -arm slots, pole roofs, scarfing of A-poles, struts, or any other purpose, the exposed surface must be liberally treated with "Creosote and Tar," so as to protect the exposed wood. This mixture consists of two parts of Creosote and one part of Coal Tar.

6. Dimensions and Weights
Wood poles are stocked in four classes, viz., "Extra light," "Light," "Medium" and "Stout"; the lengths and diameters of each class are given in Tables 1 and 2, and on card TE706. For special situations where extra-stout poles are required, poles above the average dimensions can be selected when a special note is made on the requisition. The tables also give approximate dead weights for guidance in construction work. These weights refer to Scots Pine poles, creosoted by the Ruping process.



Diameter at top

Maximum diameter at 5ft. from butt end Approx
Minimum Maximum
18ft. 4in. 5in. 5in. 0.9cwt
20ft. 4in. 5in. 5in. 1.0cwt
22ft. 4in. 5in. 5in. 1.2cwt



Light Medium Stout
Diameter at top Minimum diameter at 5ft. from butt end (in.) Approx
Diameter at top Minimum diameter at 5ft. from butt end (in.) Approx
Diameter at top Minimum diameter at 5ft. from butt end (in.) Approx
16,18 5 5 6 1.0 - - - - - - - -
20 5 5 6 1.3 - - - - - - - -
22 5 5 6 1.6 - - - - - - - -
24 5 5 6 1.9 5 6 8 2.5 - - - -
26 5 6 6 2.1 5 7 8 2.5 - - - -
28 5 6 7 2,4 5 7 8 3.2 7 9 10 4.8
30 5 6 7 2.7 6 7 8 3.7 7 9 10 5.6
32 5 6 7 3.0 6 7 9 4.2 7 9 11 6.3
34 5 6 7 3.3 6 7 9 4.7 7 9 11 7.0
36 5 6 7 3.7 6 7 9 5.3 7 9 11 7.8
40 5 6 8 4.6 6 7 9 6.5 7 9 12 9.4
45 5 6 8 5.8 6 8 10 8.3 7 10 13 11.6
50 5 7 9 7.2 6 8 11 10.3 7 10 13 14.4
55 - - - - 7 8 12 12.4 8 10 14 17.3
60 - - - - 7 8 13 14.6 8 10 15 20.7
65 - - - - 7 9 14 18.3 8 10 16 24.3
70 - - - - - - - - 8 10 17 28.1
75 - - - - - - - - 8 10 17 33.7
80 - - - - - - - - 8 10 18 40.9
85 - - - - - - - - 8 10 20 49.7

1. No 65, 70, 75, 80 or 85 foot poles were purchased after 1960.
2. After 1960 8lb of creosote was retained per cubic foot of pole and therefore the poles were slightly heavier.

7. Poles are conveyed by rail at "String measurement" weights and, by road or water, usually on a "dead weight" basis. Instructions for ascertaining these weights are given in STORES, Workmen's Procedure, K0015. When the weights cannot be conveniently ascertained, the tables shown on card TE706 may be used; the table of average "string measurement" weights is also contained in Consignment Voucher Books C910 and TE1009.

8. Distinguishing Marks
Full details of the various identification marks on poles are given in STORES, Workmen's Procedure, F 0012. The principal items affecting external construction staff are as follows:-

  1. On the butt. Poles are stamped on the butt with their stock length in feet; with either 1, 2, or 3 crowns, to indicate the class of pole - one crown for Extra Light or Light, 2 crowns for Medium, and 3 crowns for Stout; with two code letters, indicating the Creosoting Depot and the Supplier; and with two letters which are the initials of the Inspecting Officer.

  2. At five feet from the butt, figures representing the cubical contents of the pole (string measurement - calculated as indicated in STORES, Workmen's Procedure, K0015) are scribed on the surface.

  3. At ten feet from the butt, the letters G.P.O. are cut. Immediately below these are cut the length and class of pole (XL or L or M or S) and, below this again, the last two figures of the year of applying the preservative treatment. In addition, special identification marks and letters may appear if the timber is other than Scots Pine, or is treated by other than the Ruping process of creosoting (see table 3).


The top of the letters G.P.O. are placed 10ft. from the butt, and immediately below the letters the length and class markings; and below that again two figures denoting the year of application of the preservative process. The following markings would indicate a Scots Pine pole of the light class 30ft. long and creosoted in 1947.

G. P. O.
30 L

When a non-standard species or preservative process is used, the appropriate code letters are marked below the date figures.

9. Special observations of certain poles
Poles which bear identification marks other than K, R, or A (see para. 8), are to be kept under observation, and, for this reason, such poles should not be removed without the sanction of the E.-in-C; extra care should also be exercised when working on them.

10. When poles "under observation'' are recovered or renewed owing to failure by decay or otherwise, all the letters and figures which appear at the ten-foot point as well as those on the butt - if this has been withdrawn from the ground - should always be quoted in the relative records and reports.

11. Testing the condition of poles in situ
In-complete seasoning, had perforce to be given to the timber during the War period, and the condition of K poles bearing the dates 1914-1920, particularly at the ground line, should be determined whenever it is necessary to ascend them or when the periodic examinations are made (see Rules for Workmen, paras. 212 and 248).

12. When it is desired to ascertain the condition of a pole, the following considerations should be applied. The appearance should be noted and the date observed -to determine, for example, whether it falls within the period 1914-1920; but it should be remembered that a badly-weathered surface may often cover a sound interior, and that many poles remain sound for much more than 40 years, the average age ascribed to creosoted Scots Pine poles. Practical tests are of more importance, therefore, and a ready test is to strike the pole with a hammer at two or three points. If a good "ring" is the result - i.e. if it does not sound dead or hollow the pole can be regarded as satisfactory.


13. If the hammer test indicates that the pole is of doubtful condition, the suspected part should be tested by prodding with a screwdriver, penknife or any other pointed tool which may be available. When considered necessary for the purpose of this test, the soil should be dug out for a depth of 12 or 18 inches. Decayed timber on the outside of the pole is readily detected in this way.

14. A further test of a doubtful pole can be made with a "Tester, Timber," which is available and may be held on the tool list of a Sec. Engr. or on that of his assistant. The tool is illustrated in Fig. 1 and consists of a hollow auger A, a handle B, and an extractor C. The auger is used to cut out a section of wood, about one-eighth of an inch in diameter, equal in length to the depth bored; a specimen section is illustrated by Fig. 1, D. After boring to the depth required and before withdrawing the auger, the thin steel core-extractor C should be inserted in the auger to its full depth, approximately, keeping - the convex side at the point in contact with the hollow shaft. The auger should then be withdrawn and, finally, the extractor pulled out concave side uppermost, bringing with it the section of wood required. With sound timber the borings are hard, but if the timber has decayed, portions will be of a powdery character. Holes should be as few as possible and, to prevent decay setting in at these points, they should be bored in a slightly upward direction, and afterwards blocked up by the insertion of  "Plugs, Creosoted." These are wood plugs 2in. long, with a slight taper at one end, see Fig. 1, E.

15. Stacking
Poles should always be stacked carefully, and must not rest upon the ground ; creosoted timber may with advantage be closely piled, but untreated poles and Rupingized poles required for painting should be stacked so as to allow free circulation of air among them. A clear space of 9 inches should be provided between the lowest poles and the ground. The poles must not be stacked upon diseased or decaying wood; scrapped recovered poles, or portions thereof, form a suitable staging for a pole stack, and are also suitable for use as vertical posts to segregate poles of approximately the same length and/or class, so facilitating identification and handling. (See STORES, Workmen's Procedure, F0011).

16. Poles stacked or laid out on the road side should be so placed that they are not dangerous to traffic or to other users of the road, and precautions should be taken by fastening the poles together or to standing poles by means of wire - to prevent mischievous persons moving them.

17. Freshly-creosoted poles
Normally, the stock of creosoted poles at a Depot allows a suitable drying period to elapse between treatment and issue. Occasionally, however, when demands are heavy, the stock may become so reduced that wet poles have to be issued. In such cases, the delivery notes will be endorsed "Freshly Creosoted," so that steps may be taken to provide extra protection (sacking, etc.) in handling the poles (see STORES, Workmen's Procedure, B0021).

18. Painting.
Rupingized poles are not usually dry enough to be painted successfully until they have been weathered for at least six months after creosoting. Requisitions for poles that are to be painted soon after erection should therefore be endorsed "For Immediate Painting," so that the Stores Dept. may issue well-weathered poles (see STORES, Workmen's Procedure, B0021).

Pole Testing procedure


Pre-cut Pole chart


Engineering Instructions
Issue 1, 19.7.37

The Carrying Capacity of Overhead Pole Lines

1. General
The number of wires which a pole-line will carry with safety depends upon:-

  1. the amount of shelter from high winds which is afforded by surrounding buildings or trees or by the undulations of the land,

  2. the staying facilities available, and

  3. the extent of the deviation of the line at angles.

Detailed consideration of the subject is given in C1110; the following paragraphs give instructions which will meet the conditions most frequently encountered in practice.

2. Main lines
Stout Poles should be used for heavy main lines and every fifth pole should be an "A" pole (see C3251). In addition, staying, both longitudinal and transverse "Wind," should be resorted to in accordance with D 3001 and D 3026. The average span should be 55yds., but, in situations which are known to be abnormally exposed to wind, snowstorms and ice, such as over high moorland or along the coast, consideration should be given to reducing the span to 40 or even 30yds. The E.-in-C. (Cnl) should be consulted in such instances.

3. Subsidiary lines
The average span of medium and light pole-lines may be taken as 63yds.

4. Normal Situations - Straight sections of un-stayed line
The number of wires which can be carried with safety in a normal situation, without staying, is shown in Table 1 for different gauges of wire and for each of the classes of pole used.

5. The line to which the figures in the above table apply is assumed to be straight, and to be across average open country. A steady wind of 80 m.p.h. is allowed for, with no ice on the wires, and a factor of safety of 4 is used. Standard span lengths, namely 63yds., for LIGHT and MEDIUM and 55yds. for STOUT poles, are assumed.

6. To find the carrying capacity of LIGHT or MEDIUM poles for span lengths other than 63yds., multiply the above figures by 63 and divide by the length (in yds.) of the span concerned. For a line of STOUT poles, multiply the figures shown by 55 and divide by the length (in yds.) of the span concerned.

7. As an aid in memorizing the capacities of the various poles, the following method is suggested:-

  1. Note and remember the capacities of the LIGHT Poles,

  2. Then an average MEDIUM pole will carry twice as many wires, and

  3. An average STOUT pole will carry four times as many wires.

8. Lines fully stayed with angle and transverse stays
Double the capacities of Table 1 may be carried, but the angle poles should receive special consideration. At angles where the "pull-on-pole" does not exceed 10ft., the heavier of the poles used for building the line should be employed, but at greater angles the poles should be one class heavier than those used on the rest of the line, if the limiting number of wires for the lighter poles is likely to be approached. For terminal poles or at angles where the "pull-on-pole" exceeds 30ft. the provisions of D3001; as regards staying, must be strictly followed. Otherwise the poles erected must be two classes heavier than those used on the remainder of the line.

IMPORTANT NOTE: Strict adherence to these rules will ensure that the difficulty of maintaining the regulation of the line-wires, due to an unstable pole-line, is minimised.


Type and length
of pole
No. of wires carried with safety in normal situations
40lb 70lb 100lb 150lb 200lb 300lb 400lb
LIGHT poles 14 10 8 - - - -
MEDIUM poles 28 20 16 13 11 8 7
STOUT poles Up to 40 ft. 65 47 38 30 27 21 17
STOUT poles 45 and 50 ft. 54 39 32 25 22 17 14
STOUT poles 55 ft. 43 31 25 20 17 13 11

9. Clearances
The foregoing rules are all conditional upon the necessary clearance over roadways, etc., being given (see B1301).

10. Sheltered situations, such as are found in urban districts. On straight sections of line, the figures of Table 1 may be doubled and the transverse stays omitted, but, at angles where the deviation is appreciable, the rules laid down in para. 8 should be followed.

11. "Storm" situations
For positions exposed to storms, the figures of Table 1 may be used, but, in addition, adequate transverse and longitudinal staying must be given and the length of span should be reduced as indicated in para. 2.

12. Lines carrying wires of differing (mixed) gauges Table 2
The number of wires of each gauge should be multiplied by the relevant factor from Table 2, and the resulting numbers should then be added together. This will give a figure representing the total number of line wires, expressed as equivalent 40lb. conductors. The "40lb." column of Table 1 may then be used to determine the class of pole necessary to carry the line.


Weight of wire per mile Factor giving equivalent number of 40-1b. wires
Bare Wires - 40lb 1.00
Bare Wires - 70lb 1.37
Bare Wires - 100lb 1.70
Bare Wires - 150lb 2.18
Bare Wires - 200lb 2.52
Bare Wires - 300lb 3.15
Bare Wires - 400lb 3.68
Bare Wires - 600lb 4.54
Insulated Wires - 70lb 4.4
Insulated Wires - 150lb 5.15
Insulated Wires - 200lb 5.6
Insulated Wires - 300lb 6.2
Insulated Wires - 400lb 6.7

13. Insulated Wires (L & P.B.J.) Table 3
The carrying capacity of lines composed wholly of covered wires may be obtained directly from Table 3, without recourse to Tables 1 and 2.


Type and length
of pole

No. of wires carried with safety
70lb 150lb 200lb 300lb 400lb
LIGHT poles 4 3 - - -
MEDIUM poles 6 6 5 4 4
STOUT poles Up to 40 ft. 15 13 12 11 9
STOUT poles 45 and 50 ft. 12 11 10 9 8
STOUT poles 55 ft. 10 9 8 7 6

Engineering Instructions
Issue 2, 29.6.36

Introduction for General Use

1. General. The use of slotted poles will eventually be discontinued and, in due course, all poles, except Extra eight, will be pre-cut as described in this Instruction. The execution of all cutting and boring, prior to creosoting, will lessen the chances of decay; arming will be simplified, a stronger job will result, and the tendency for arms to get out Lf alignment will be reduced.

FIG. 1

2. At the Pole Depots, poles will be "scarfed", to provide a flat surface 3 to 4ins. in width; bored for arm-bolts; and trimmed to a 90 apex at the top, as shown in Fig. 1.

3. For the present, the scheme will be restricted to Light and Medium poles. There are considerable stocks of Stout poles, and it is uneconomical to treat these further; stout poles should, therefore be slotted as in the past. Extra Light poles will be issued with roof slopes cut, and holes bored, for a pair of swan-neck spindles.

4. Availability of pre-cut poles
Supplies of 16ft. to 20ft Light, and all sizes of Medium, pre-cut poles will become available for issue to the South Wales District, and to Bristol, Taunton and Plymouth Sections during the next few months. Requisitions will be met by the issue of ordinary poles until stocks are exhausted; pre-cut poles will then become the standard issue. Pre-cut Light poles, 22ft. long and over, are already being issued in these areas.

5. Supplies to other Districts will follow and when suitable arrangements are made by the various Pole Depots. The Stores Dept. will notify Engineers as and when they may expect the issue of pre-cut poles to commence.

6. Special arrangements for London, E. and S.E. Districts
In view of the large number of finials used in London and the neighbourhood, arrangements will be made for a stock of pre-cut poles with flat tops bored for finials, to be held at appropriate Pole Depots. (These stocks may be drawn upon by the S.E. District and the Southend and St. Albans Sections of the Eastern District as well as by the London Engineering District). Requisitions should indicate that flat tops are required.

7. Scarfing and Boring locally
It will occasionally be necessary to scarf and bore a pole locally, e.g., where cross-arming is required. Suitable tools for scarfing the pole are an Adze, Carpenter's or a Draw Knife and a Plane, Jack 2in., the latter being used to true-up the surface so as to obtain vertical alignment of the arms. The flat should be cut to a uniform depth through its length, as shown in Fig. 1. A 5/8in. screw auger or bit should be used to bore the pole; no larger size may be used. A chalked line or a straight-edge will be required when determining the positions of the holes and special care should be taken to ensure that the holes are central on the pole, accurately in line, correctly spaced, and perpendicular to the flat surface. The freshly-cut surfaces should be treated liberally with "Creosote and Tar".

8. Pole roofs
These are not necessary on pre-cut poles. As the roof-slopes are cut prior to creosoting, the tip of the pole presents a thoroughly creosoted surface to the weather. In certain circumstances (e.g., for uniformity, or to meet the wishes of Wayleave Grantors), it may be desirable to provide a roof, or less frequently a finial. The decision in such is left to the discretion of the Sec. Engr.

9. Where a roof is to be fitted
A flat, 1in. wide, should first be cut or planed on the ridge. Where a finial is required, other than on a flat-topped pole, the pole should be cut off square and the finial fitted in the usual way. In either case, the exposed timber should thoroughly coated with "Creosote and Tar".

10. when a saddle is required, a 1 flat should be cut on the ridge; a roof need not necessarily fitted. If saddle stays are required and a roof is
not provided, the hardwood wedges should be omitted and the stays suitably bent to fit close against the sides of the pole.

11. Arming of pre-cut poles is described in C3552.


Pole type availability - 1983

The following poles were available:-
Light - 6, 7, 8, 8.5, 9, 10, 11 and 12 metres.
Medium - 7, 8, 9, 11, 12, 13 and 15 metres.

Metal Poles


C 3280
Issue 4, 30.8.51

Sheet-steel Type

1. General
This Instruction describes the assembly and erection of, and the fittings for, Sheet-steel poles, which should be used whenever practicable in lieu of wood poles until stocks are exhausted; no further provision of steel poles is contemplated.

2. Types and sizes
The sheet-steel popes ace of two types, and are available in the following lengths under the Rate Book description indicated:-

Poles, Sheet-Steel: Arm Type:-
18 ft. XL
20 ft. L
22 ft. L
24 ft. L
28 ft. M
29 ft. M

Poles, Sheet-Steel: Distribution Type:-
28 ft. M
29 ft. M

3. The poles are equal in strength to the corresponding class of wood poles and should be regarded as alternatives to such poles in all conditions of use with the following exceptions:-

  1. Arm type D.P.s [except when additional sections (see par.4) are fitted to distribution-type poles].

  2. Strutted poles.

  3. Poles in industrial atmospheres where galvanized ironwork is known to have a short life.

  4. Poles set in peat or other soils in which ironwork is known to corrode.

4. Additional top sections are available for fitting to the existing top sections of medium poles (Distribution type). The sections increase the height of the pole by 4ft. and allow the pole to be used as an armed or ring-type D.P. or as an armed line pole.

5. Electric Shock
Slight shocks may be received while working aloft, when any exposed part of the body comes into contact with the wires. The shocks are not of a serious nature but it is advisable to keep clear of the wires until the safety belt has been fastened round the pole.

6. Description
Each pole consists of galvanized tubular sections, tapering in. per foot and formed from hard rolled mild steel sheets with lapped and welded longitudinal seams. Each section is 6ft. 6in. long with the exception of the butt section which may be shorter to give the overall length required. A galvanized cap, which is a push fit, closes the end of the top section.

7. The poles are supplied as a nest of sections bound together by a steel tape. The cap is supplied in a separate container. Provision is made for the attachment of pole steps and other fittings by aluminium alloy "Rivnuts" (see Fig. 1) which are fitted during manufacture. Care should be taken to ensure that only the B.S.F. bolts provided are used with the Rivnuts (see pars. 19 and 20).


8. Arm type poles of the medium and light :lass are provided with six arm bolt holes, 12in. apart in the top section. Extra light poles are
provided with two arm bolt holes. The holes are reinforced by steel tubes welded into the walls of the pole as shown in Fig.2. The Rivnuts allow for the attachment of steps on the medium poles at the positions shown in Fig. 2. They are provided on both sides of the pole to enable two steps to be fitted at the same level, if necessary. On the 24ft light poles the steps are 4ft. from the top of the pole. On later supplies of 22ft. and 24ft. light poles, additional Rivnuts are provided for a step 2ft. 9in. from the top. This single step is for use while fastening the safety belt; by placing one leg over the step the hands are free for securing the belt. No provision is made for steps on the 20ft. light and 18ft, extra light poles, as the pole head can be reached from a ladder.


9. Distribution type poles are provided with Rivnuts at the positions shown in Fig. 3 for the attachment of a ring-type pole head and steps. A plate is provided on the cap for a terminal block. In addition, two cable entry holes are provided in the bottom section, and one exit hole at the top. A clip for fixing the cable to the pole is fitted above the exit hole. Bolts for the fixing clip and for attaching the pole head are supplied with each pole. No facilities are provided for attaching arms.


10. Additional top sections, 4ft. 8in. long, for fitting to the existing top sections of medium poles, are provided with distance tubes to enable four arms to be attached and also with rivnuts suitably placed for attaching a pole head and one pole step. Two cleats to enable a cable to be attached are supplied fixed to each section.

FIG. 4

FIG. 5

11. Special fittings
The pole has been designed, as far as possible, to allow for the use of standard fittings, but it necessitates the use of the following special items, which should be requisitioned separately as required.

  1. Pole Steps. Steps are of the cantilever type with double webs, pressed from mild steel sheet and provided with a non-skid tread (see
    Fig. 4). The steps are designated in the Rate Book as "Steps, Pole, No.2" (two B.S.F. fixing bolts are included).
    NOTE:- Pole steps for use with wood poles will, in future, bear the title "Steps, Pole, No.1"

  2. Arm seats. This item (see Fig.5) is fitted to the arm type poles to give the wood arms lateral stability in the absence of a pre-cut surface or slot, and is shown in the Rate Book as "arm-seats".

  3. Clips, Pole, Sheet-steel, Nos. 1 and 2 for use on light and medium poles respectively. The clips consist of four bolted sections and a bracket containing a 5/8 in. bolt, nut, and washer. They are fitted around the pole over a "Collar, Split, Sheet-steel" (see Figs. 7, 10 and 11). The bolt in the bracket is for the "Bracket No. 12, 13, or 20", used for aerial cable suspension wires.

  4. Collars, Split, Sheet-steel, Nos. 1 to 4 are similar to a section of the pole split down one side, and are fitted by springing them around the pole. They are used to strengthen the pole at a point here a clip or stay wire is attached, or where suspension wire is terminated. The collars are wade in four sizes, Nos. 1 and 2 are for use on light poles, and Nos. 3 and 4 on medium poles. Collars Nos. 1 and 3 are 6in. deep and contain two slotted holes situated diametrically opposite to each other to allow the fitting of an arm bolt through them. Collars Nos. 2 and 4 are 3 in. deep and do not contain slotted holes.

    Collars Nos. 2 or 4 should be used where a clip or over-road stay only is required at a position where no arm is fitted or anticipated. In all other cases, a Collar No.1 or 3 should be used where the number of attachments is such that they cannot all be accommodated on one collar; additional collars should be fitted above or below the first one.

  5. Pole Heads, Ring-type, Split, 15 way.  The brackets of this pole head are fitted with Rivnuts provided on the poles. Requisitions should be endorsed "for Sheet-steel poles", to ensure that the correct item is supplied.

Fig 6

Fig 7. CLIP, POLE. SHEET-STEEL No. 1 and 2

12. Assembly
The pole should be assembled on site by laying the sections horizontally and joining together the tapered sections. The overlap of the sections varies from approximately 9in.at the top to approximately 14in. at the bottom. Assembly should be commenced with the butt section and procedure is as follows:-

  1. Place the large end of the butt section against a flat wood surface, e.g. a stayblock placed against a tree, existing pole, wall, or a crow bar driven into the ground. Raise the smaller end a few inches off the ground with a suitable piece of timber placed under the section and about 1ft. 6in. from the smaller one.

  2. Clean the surfaces that are to overlap,
  3. Slide the second section on to the out; section with the longitudinal seam of one section diametrically opposite to that of the other.

  4. Remove the piece of timber support in; the small end of the butt section to a point roughly 1ft. 6in. from the large end of the second section (see Fig. 6)

  5. Drive the second section on to the butt section by a few moderate blows applied with a sledge hammer to a piece of timber interposed between the hammer and the pole section. Hammering should cease, as soon as the movement of the second section is inappreciable.

The above operations (b) to (e) inclusive, should be repeated for each section until the pole is completely assembled. Fig. 6 illustrates the assembly of the first two section. A painted alignment mark will be  found on the top section - this should be carefully registered with the weld seam on the adjoining section to ensure alignment of fittings.

13. Additional top sections should be used with 28ft and 29ft. medium Distribution-Type poles if required. When used for ring-type distribution it should be ensured that the overhead cables are evenly distributed  radially otherwise the lengthened pole will bend.

14. The overlap of the extra section will extend slightly below the upper Rivnuts of the existing top sections and before it is fitted these Rivnuts should be removed by driving a sharp cold chisel between the Rivnut and the pole.

15. When assembling the pole, the existing top section should be turned through 45 so that the Rivnuts for two of the four pole steps fitted at the same level will be in line with those provided for steps on the lower sections. The extra section should be located so that the painted line on the larger end is in line with the welded seam of the lower section.

16. Additional Rivnuts should be inserted, as described in pars. 23 to 26 in the existing top section, so that steps can be fitted at 18in. intervals from the existing steps to the point where the extra section overlaps.

17. The existing pole cap should be used on the top of the extra section. Three Rivnuts spaced 120 apart should be fitted along the centre line of the vertical face of the cap and any slackness in the fit taken up by tightening a bolt fitted into one of the Rivnuts.

18. Attachment of fittings
Arms should be attached in the normal manner as described in C3552 except that the arm-seat should be interposed between the pole and the arm. The arm-seat should be placed with its folded edges towards the arm, and the arm bolt tightened until the flat side of the arm-seat assumes the curvature of the pole (see Fig. 5).

19. Pole Steps should be fitted in the positions described in C3151. They should be fixed to the pole only with the two in. B.S.F. bolts supplied with the steps. To facilitate fastening the safety belt when aloft (see par. 8) and to prevent the fastened pelt slipping down the pole, an additional step should be provided 2ft. 6in. above the existing steps used for standing on during working operations. Where Rivnuts for such a step do not exist they should be fitted as described in pars. 23 to 26.

20. Ring-type Pole Heads are fitted to the pole by the eight 3/8in. B.S.F. bolts supplied with the pole. A 8in. galvanized washer, obtained locally, should be inserted under the head of each bolt.

21. Terminal Blocks should be attached to the plate welded to the pole cap with four No. 1 or 2 B.A. brass countersunk-head screws and nuts which should be obtained locally. The plate is drilled to accommodate "Blocks, Terminal, No. 8 or 9".

22. Cabling
Before a pole is erected, a length of "Wire, Galvanized, 60lb.", should be passed through the inside of the pole via the cable-entry and exit holes, and after the pole has been erected, the wire should be used for drawing-in the cable.

The terminal block should first be fitted to the cable, which should then be taken to the top of the pole. The sealed end of the cable should be attached to the draw wire and fed through the exit hole, care being taken to avoid damage to the sheathing. To prevent water entering the hole, the cable should be wrapped with adhesive insulating tape at the point where it will remain in the mouth of the exit note. After securing the terminal block to the pole, the cable should be fastened under the clip provided.

23. Fitting Additional Rivnuts
The rivnuts are Known as "Rivnuts, B.S.F., 3/8in. - 100 anodized" and should be obtained by local order from Messrs. Linreaj Ltd., Stirling Works, Cox Street, Birmingham, 3. The tools required for fitting the Rivnuts ere as follows:-

  1. 3/16in. and 3/8in. diameter drills.

  2. 15/32in. maximum diameter tapered reamer.

  3. Rivnut, Upsetting Tool, wrench Type, 3/8in. B.S.F.

24 . To secure a satisfactory fixing for Rivnut, it is essential that the made for it should not exceed 15/32in. Should difficulty arise in obtaining a reamer of maximum diameter should be obtained and arrangements made for the cutting edges at the large end to be ground off to provide a maximum diameter of 15/32in. The diameter of the smaller end of the reamer should not exceed 3/8in.

25. It will be generally found that one upsetting tool and one reamer per area will meet requirements.

26. The position of the Rivnut should be carefully marked with a centre punch and a 3/16in. diameter hole drilled. The hole should then be enlarged, first with the 3/8in. diameter drill, and then with the reamer. The Rivnut should be inserted in the hole and upset as indicated in the instructions supplied with the tool by the makers.

FIG. 8

27. Attaching Saddles
When saddle wires are required "Saddles, Galvanized", should be fixed to the cap and a "Stay, Saddle" fitted as shown in Fig. 8. The lugs of the saddle should be placed in a vice and bent to fit the curvature of the cap. Rivnuts should be fitted to the cap to take the bolts which pass through the upper fixing holes of the lugs. The "Stay, Saddle" should be bent to the shape shown and the ends fixed to the bolts holding the top arm on the pole.

28. When two saddle wires are required, a "Bolt No.6" should be passed through the saddle before it is bolted to the cap. When a single saddle wire is to be fitted, the nut of a "Spindle No.4" should be placed in the cavity underneath the saddle so that the spindle when subsequently fitted to the saddle will engage with the nut.

29. Attaching Reflectors Disc.
Two Rivnuts, 5in. apart, should be fitted to the pole at the positions indicated in C3161. The two fixing holes in the reflectors should be enlarged to 7/16in. diameter and 3/8in. B.S.F. bolts, 2in. long, used to fix the reflector to the Rivnuts.

30. Erection of Sheet-steel poles
The holes for the poles should be prepared as described in C 3176. When handling the assembled and fitted poles, it will be found that, unlike wood poles, they are inclined to be top heavy, depending on the number of arms etc. fitted. The poles do not normally need any special plat:; at the butt on which to rest, out, in soft ground, where a stay is to be fitted, or is Anticipated at a later date, the pole should rest on a concrete slab, or other flat, solid, material.

31. Staying. Terminal, Transverse, Line or Angle Stays
A "Collar, Split, Sheet-steel No. 1 or 3" should be fitted at the ultimate resultant load point, and the stay wire made off in the normal manner as shown in Figs. 9 and 10.


32. Horizontal Stays should be made off in the normal manner over a suitable collar.

33. Aerial cables
The suspension wire should be attached as follows:-

  1. True and False Terminations should be made in the normal manner using a suitable collar between the suspension wire and the pole

  2. Brackets Nos. 12, 13 or 20 should be attached by using "Clips, Pole, Sheet-steel", and "Collars, Split, Sheet-steel" (see Figs. 9, 10 and 11).

Fig. 11

34. Numbering and Marking of Sheet-steel Poles.
The labels and methods of numbering and marking sheet-steel poles are described in C 3161.

Steel Pole type availability - 1983

These poles are supplied fully assembled.

Pole, Hollow Light 8.5metres type A.
Steel, two diameter round section, with longer section at base.

Pole, Hollow Light 8.5metres type B.
Sheet steel, octagonal section at butt, continuously tapered, circular at tip.

Fibre Glass Pole

Designed not to be climbed these poles are used when in close proximity to railings, glass topped walls or other dangerous locations.

There is a trap door at chest height that allows access to the Block terminal No. 71 and a metal ring with holes in it, which is fixed to the inside of the pole body.  The Block terminal hangs on a hook inside the pole and can be lifted out of the pole to work on.

The pole is capped with a curved exit hole.  Dropwires enter the pole over the curved edge of the pole cap and are clamped, using dropwire clamps, to the internal metal ring.

The dropwire is fed into the pole in the following manner:-

  1. A Line Sash No. 2 is fitted with a snap hook, with a rigging weight attached.

  2. Three Rods, Duct No. 2 are connected together and a rigging head is attached at at the top end.  The rigging head has a pulley installed within it.

  3. The sash line is fed through the rigging head until the rigging weight is up against the Rigging Head.

  4. The whole assembly is now inserted through the access door of the pole, making sure the sash line is held tight.  The rods are pushed upwards until they reach the pole top and the rigging head drops over the edge of the pole cap.

  5. The sash line can now be released and the line will drop to the ground due to the rigging weight.

  6. The rods can be withdrawn, leaving the sash line in situ.

  7. The rigging weight is removed and the dropwire (or at a road crossing, another sash line) is tied to the snap hook.

  8. The sash line is now pulled back through the access door until the dropwire appears at the trap door.

  9. The dropwire is pulled taught and connected to a dropwire clamp, which is located on the internal ring.

Pole type availability - 1983
Pole, Hollow, Light 8.5metres type C.
This pole was made of Glass Reinforced Plastic and had a circular section that was continuously tapered.


Rigging Head No. 1A


Rigging Weight No. 1A



BACK Home page BT/GPO Telephones Search the Site Overhead Construction Quick Find All Telephone Systems

Last revised: June 18, 2023